The invention relates to a device for suctional intake and forced discharge to a patient of one or several treating gases, or a mixture thereof. One of the gases is taken from a non-pressurized system. The device comprises a self-expanding lung-venting bladder, i.e. a bladder which automatically resumes its original shape after a compression. The bladder has an inlet provided with a check valve enabling treating gas such as atmospheric air and/or another gas to be sucked into the bladder, and an outlet leading to the patient, for example via a three-way breathing valve connected to a breathing mask or similar device either directly or via a connecting conduit. Such a self-expanding bladder fundamentally operates as follows:
When the bladder is compressed, the gas contained therein is expelled through the outlet valve and further to the respiratory ducts of the patient via the breathing mask. Thereafter the bladder is released and regains its original shape by virtue of its self-expanding property thereby causing a subatmospheric pressure to be formed within the bladder. Due to this subatmospheric pressure the bladder will again be filled with gas through the inlet valve whereafter a new insufflation may be performed.
In venting systems of this type it is often desirable to supply, in addition to the main gas fed through the suction valve, a treating gas, such as oxygen or narcosis gas. It is also desirable that the main gas and the additional gas be mixable in arbitrary proportions. In known systems such a gas is added via a separate valve opening into the bladder. As such additional gases are supplied under relatively high pressure (1- 3 atmospheres) particular safety measures must be taken to prevent the patient from being exposed to harmful excess pressures due to the supply of the additional gas. This problem has, so far, not been solved in a satisfactory way.